Treatment of partially oxidized hydrocarbons



'April 16, 1957 w. E. THOMPSON 2,789,123

TREATMENT OF PARTIALLY OXIDIZED HYDROCARBONS Filed Aug. 25, 1955 Solvent andGas Solvent 28 Primary I Solvent \9 Solvent Oxidation Extraction Removal Zone Zon Zone l2 v Oxygeng Containing (V I? t Finer Flue Gas 5 0x en Containing 27 Y9 M Flue Gas i I Air Oxygen- Containing 3| l3\ Flue Gas l6 Air l\ l 1 Storage Storage Zone Zone 40 2 Air Air INVENTOR.

WILLIAM E. THOMPSON sQ-ia W ATTORNEY United States Patent TREATMENT OF PARTIALLY OXIDIZED HYDROCARBONS William E. Thompson, Wallingford, Pa., assignor to The Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey Application August 25, 1953, Serial No. 376,375 9 Claims. c1. 260 -452 This invention relates to the treatment of partially oxidized hydrocarbons and more particularly to the maintenance of partially oxidized petroleum at elevated temperatures without excessive discoloration.

It is known in the art to partially oxidize hydrocarbon materials, e. g. petroleum lubricating oil, foots oil, wax, etc. to obtain carboxylic acid materials suitable for various uses. The partial oxidation product mixture generally contains unoxidized hydrocarbon material, carboxylic acids, and other types of oxidation products. For various reasons, it is frequently desired to maintain the product mixture or some component thereof at elevated temperature, e. g. about 100 F., for a substantial period of time. For example, in the case of an oxidation product mixture obtained from wax, which product mixture is solid at room temperature, the product mixture is often maintained at a temperature above its melting point for substantial periods of time while the product mixture is being transported, stored, packaged, etc., after having been removed from the oxidation zone.

Another instance in which oxidized hydrocarbons are maintained at elevated temperature for substantial periods of time is in the removal of volatile solvent from oxidized hydrocarbons which have been admixed with the solvent. It is known to contact partially oxidized hydrocarbon product mixtures with various selective solvents, e. g. pentane, petroleum ether, gasoline, naphtha, aliphatic. alcoholssuch as methanol, ethanol, isopropanol, etc. ketones such as acetone,'methyl ethyl ketone, etc., lower fatty acids such as acetic acid, other solvents such-as pyridine, etc., or mixtures of solvents, in order to selectively extract certain constituents of the productrnixture. In removing solventfrom either extract or raifinate, it is common practice to distill 01f the solvent from. the constituents of the oxidation product mixture. In such distillation,.the product mixture is subjected. to elevated temperatures suflicient to volatilize the solvent. Also, the preceding solvent extraction may have been conducted at elevated temperature.

A serious problem arising in the maintenance of partially oxidizedhydrocarbon product mixtures at. elevated temperatures for substantial periods of time is the discoloration ofthe product mixture. Elevated temperatures, particularly those in excess of 150 F., have 'a substantial, and often great, discoloring efiect on. a partially oxidized hydrocarbon product mixture. The present invention is directed to the inhibition or prevention of such discoloration.

According to the present invention, partially oxidized hydrocarbon product mixtures, after removal from the oxidation zone, are maintained at elevated temperature While being contacted with free-oxygen containing gas, the latter being introduced into contact with the product mix ture for the special purpose of preventing the excessive discoloration which. would otherwise occur at the elevated temperature. It has been found that the effect of the free-oxygen containing gas somehow counteracts the discoloring tendency of the elevated temperature.

The treatment of the present invention is conducted ice under conditions which provideonly slight, if any, additional oxidation of the oxidation product mixture. The rate of introduction of oxygen islow, e. g. less than 150 cc. of oxygen per minute per 1000 grams of oxidized wax, and generally considerably lower than the rate of. introduction of oxygen duringthe-partial oxidation whichproduced the oxidation product mixture. Some further oxidation of the product mixture will generally take place during the treatment according to the invention, but. it will generally be slight and willusually not increase the saponification number of the product: mixture by more than 5 mg. of KOH per gram; usually the-saponification number increase will not: be greaterthan 1 mg. of KQH per gram in av 10-20 hour period. 7

The method ofthepresent invention is-advantageously employed with any normally liquid or solid partial oxidation. product mixture obtained from hydrocarbon material, and particularly withpartial oxidationproductsof petroleum. The partial. oxidation may have been conducted in any. suitable manner. Commonly employed oxidation conditions for petroleumv materials such as lubricating oil, foots oil, paratfin, microcrystalline. wax, etc. include. a temperature in. the range from. 200 F. to 300 F., atmospheric or. elevated. pressure,.eg. up to. p. s. i. g., introduction of a free-oxygen containing gas, e. g. air, oxygen, ozonized air,.etc., at. a rate corresponding to an. oxygen rate withinthe range. from 200101000 ml. ofgas per 100.0. grams ofhydrocarbon per minute. Any suitable oxidation catalyst can beuseddf a. catalyst is necessary or desired, suchas the well-known. type comprising metal salts of carboxylic acids- I Y The manner of contacting, theoxidation product mixture with free-oxygen containing gas varies according to the circumstances in which the. product mixture is being maintained at elevated temperature. For example, when the product mixture is being stored in a vessel, the freeoxygen containinggas can. be advantageously introduced at the. bottom of the vessel throughsuitable distributing means such as a sparger. Or, when the product mixture is being pumped through. conduits, thefree-oxygen containing. gas can advantageously be injected into the conduits. at suitable intervals alongthe length thereof. When the product mixture is being stripped ofsolvent. in a distillation zone,.the freeaoxygen containing gas. can serve the additional function of a stripping gas,. thus aidingin the vaporization of solvent from the distillation charge. An additionalstripping gas, such as steam, can be used along with.the free-oxygen containing gas.

When the process of. the present invention is used in the distillation of. solvent from the oxidation product mixture, the oxygen content. of the free-oxygen containing gas is preferably not greater than 10 volume percent. Particularcareshouldbe taken to avoidthe formation of an explosive mixture in the distillation zone. A highly advantageousand safe free-oxygen containing gas for use in distillation. of solvent is flue gas, e. g. that obtained in the regenerationof oxidation of cracking catalyst. Such flue gas often contains small percentages of oxygen which make it suitable for use according to the invention. If it is desiredto. increase the oxygen content of the hire gas above its normal content, it can be admixed with air or oxygen in the proper proportions to produce the desired content. Generally, the oxygen content of the gas should be at least 0.1 volume percent, preferably atleast 1.0 percent.

Free-oxygen containing. gases generally'sui'table. for, use according to the invention include oxygen, air, ozonized air,.flue gas, etc. Ozone itself is regardedas a free-oxygen containing gas for the purpose of the present invention.

The temperature of the treatment according to the invention depends on the requirements forthe particular operation involved. Thus, if a normally solid oxidation product mixture is being handled in liquid phase, the temperature is at least as great as the melting point of the mixture. In a solvent extraction, the temperature may depend on the degree of extraction that is desired.

"In stripping solvent from extract or raflinate, the temperature must be great enough to vaporize the solvent under the pressure employed. Preferably, the temperature used is maintained as low as it can suitably be for the purposes of the operation involved. Generally, temperatures not exceeding 350 F. should be used. The lower the temperature, the more eifective in preventing excessive discoloration is the process of the invention. Preff erably, the temperature used does not exceed 225 F.

bon material, e. g. petroleum microcrystalline wax, is j partially oxidized in primary oxidation zone by contact with air introduced through line 11. At the conclusion of the oxidation, the molten oxidation product mixture is withdrawn through lines 12 and 13 into storage zone 14. During passage through line 13, air is injected at a low rate into the product mixture through lines 15 and 16 in order to prevent excessive discoloration of the product mixture. The number of places where air is injected depends on the length of the conduit through which the product mixture is transported. Although two such places are shown in the drawing,'one will usually be enough except for quite long conduits. Air is introduced at a low rate into storage zone 14 through line 40 to prevent excessive discoloration of the product mixture during storage.

The effiuent product mixture from zone 10 can also be passed through line 17, into which air is injected through line 18, into solvent extraction zone 19. A volafile solvent, e. g. gasoline, is introduced through line 20 and intimately contacted with the product mixture in zone 19. The mixture of solvent and product mixture is withdrawn through line 21 and filtered in filter 22 to obtain a filtrate which is removed through line 23. A flue gas containing for example about 5 volume percent oxygen, is introduced into line 21 through line 24 to prevent excessive discoloration during passage through line 21 and the filtration.

The filter cake obtained in the filtration is removed from filter 22 and melted by means not shown. The molten material, comprising constituents of the product mixture, from which other constituents have been separated by the filtration, is then introduced through line 25 into solvent removal zone 26. A flue gas containing for example 5 percent oxygen is introduced into line 25 through line 27. Solvent remaining in the oxidation product mixture is stripped therefrom in zone 26 by means of the flue gas introduced through line 33. Solvent vanors and gas are removed through line 28. The residue from the stripping operation comprises substantially solvent-free product mixture and is removed through line 29 and introduced into storage zone 30. Air is introduced through line 31 into line 29 and through line 32 into storage zone to preventexcessive discoloration during transportation and storage respectively.

The following examples illustrate the invention.

Example] A partially oxidized microcrystalline petroleum wax was maintained in liquid phase at a temperature of about F. in the presence of a manganese naphthenate catalyst in amount such that the oxidation charge contained 0.04

weight percent of manganese. The air rate during the the stripping zone.

4 oxidation was about 3000 cc. per minute of air per 1000 grams of wax. The saponification number of the oxidized wax was mg. of KOH per gram, and the color of the oxidized wax was 3 N. P. A.

After the blowing with air for 22.5 hours at 210 F., the color of the oxidized wax was 2% N. P. A. By way of contrast, when the same oxidized wax at 210 F. was blown with nitrogen for 21.5 hours, the color deteriorated to 4 N. P. A. Similarly, when the same oxidized wax was maintained at 210 F. for 21.5 hours without any gas being blown therethrough, the color deteriorated as much as or more than in the blowing with nitrogen.

The following table shows a comparison of the results obtained according to the invention with those obtained using nitrogen:

N. P. A. color Oxidized wax before heating to 210 F 3 Oxidized wax after heating to 210 F. for 22.5 hours with air 2 Oxidized wax after heating to 210 F. for 22.5 hours with nitrogen The example shows that partially oxidized microcrystalline wax can be maintained in the liquid state without decolorization at 210 F. by contacting the oxidized wax with a free-oxygen containing gas, whereas the color of the oxidized wax undergoes substantial deterioration when the oxidized wax is maintained at 210 F. in the absence of added free-oxygen containing gas.

Example 2 A partially oxidized petroleum microcrystalline wax was mixed with alkylate gasoline and the mixture filtered at room temperature to obtain a filtrate comprising constituents of the oxidation product mixture dissolved in alkylate, and to obtain as filter cake the oxidation product mixture from which such constituents had been removed.

The partial oxidation of the wax hadbeen performed under conditions generally similar to those used in Example 1, the oxidation having been continued, however, to a saponification number of about 116. The color of the product mixture was 2% N. P. A.

The filter cake obtained as described above contained some alkylate material. In order to remove this material, the filter cake was melted and introduced into a stripping zone wherein it was contacted at about 230 F. with air, which was passed through the molten oxidation product mixture at a low rate for about 8 hours. The air, carrying solvent vapors with it, was removed from The residue from the stripping operation consisted essentially of about 600 grams of substantially alkylate-free, partially oxidized microcrystalline wax having saponification number of 62.5 and N. P. A. color of 3%.

By way of contrast, the stripping operation was conducted on another portion of the same filter cake under essentially the same conditions except that nitrogen instead of air was passed through the molten oxidation product. The color of the residue was found to be too dark to measure on the N. P. A. scale.

The following table shows a comparison of the results obtained according to the invention with those obtained using nitrogen:

N. P. A. color Oxidized wax before solvent treatment 2% Oxidized wax after stripping solvent with 3 /2 air at 230 F.

Oxidized wax after stripping solvent with Too dark to nitrogen at 230 F. measure.

This example shows that solvent can be stripped from partially oxidized microcrystalline wax in the presence color occurs when solvent is stripped from the oxidized wax at 230 F. in the absence of free-oxygen containing gas.

Example 3 An experiment similar to that described in Example 2 was performed, using a flue gas in place of air as the gas which is passed through the stripping zone. The flue gas used was obtained by combustion of natural gas in a flue gas generator. This flue gas contained 7.4 volume percent of oxygen, 6.0 volume percent of carbon dioxide, and substantially no carbon monoxide.

The oxidized microcrystalline wax used had saponification number of 99, and N. P. A. color of 2%, and had been prepared by oxidizing 100 pounds of microcrystalline wax with 3 cubic feet per minute of air, the oxidation being conducted at approximately atmospheric pressure and 250 F. in the presence of manganese naphthenate and magnesium naphthenate in amounts such that the weight percents of manganese and magnesium in the oxidation mixture were 0.01% and 0.03% respectively. After mixing 910 grams of the oxidized Wax with 4 gallens of alkylate and filtering, the filter cake was heated to 210-220" F. and blown with 500 ml. per minute of flue gas for 6 hours to strip off substantially all of the alkylate, leaving about 407 grams of substantially alkylate-free oxidized wax having N. P. A. color of 4 /2-, as compared with 2 /2 N. P. A. for the oxidized wax prior to contacting with alkylate.

This example shows that flue gas containing 7.4 percent oxygen produces results generally similar to those obtained with air in Example 2, though the final color was somewhat better with air than with flue gas.

The invention claimed is:

1. Method for preparing partial oxidation products having satisfactory color which comprises: partially oxidizing normally non-gaseous hydrocarbon material in liquid phase in an oxidation zone to obtain saponifiable products; removing the products from said oxidation zone; and contacting the products at elevated temperature normally producing excessive discoloration of the products, in liquid phase with free-oxygen containing gas under partial oxidation conditions providing an increase in saponification number not greater than mg. of KOH per gram and less than the increase in saponification number provided by said partially oxidizing.

2. Method according to claim 1 wherein said products are admixed with a volatile solvent and wherein such contacting is eflected during distillation of the volatile solvent from said products.

3. Method according to claim 1 wherein such contacting is eflfected during storage of said products.

4. Method according to claim 1 wherein such contacting is efiected during transportation of said products.

5. Method according to claim 1 wherein the rate of contacting of oxygen in said free-oxygen containing gas with said products is less than about 150 cc. of oxygen per minute per 1000 grams of said products, and Wherein the temperature of said contacting is not substantially above 350 F.

6. Method according to claim 1 wherein said contacting is effected with free-oxygen containing gas as sole oxidizing agent.

7. Method according to claim 1 wherein said partially oxidizing is performed at a temperature Within the approximate range from 200 F. to 300 F. by contact with free-oxygen containing gas, the rate of contacting of oxygen in the gas with hydrocarbon being within the approximate range from 200 to 1000 cc. of oxygen per minute per thousand grams of hydrocarbon, and wherein the contacting of said products with free-oxygen containing gas is performed at a temperature Within the approximate range from 150 F. to 225 F. and less than the firstnamed temperature, the rate of contacting of oxygen in the free-oxygen containing gas with said products being less than 150 cc. of oxygen per minute per thousand grams of said products.

8. Method according to claim 1 wherein said partially oxidizing is performed in the presence of an oxidation promoter selected from the group consisting of ozone and oxidation-catalyzing metal salts of carboxylic acids, and wherein said products have saponification number of at least about mg. of KOH per gram.

9. Method according to claim 1 wherein said products are admixed with a volatile solvent, and wherein such contacting is efiected during distillation of the volatile solvent from said products, and wherein said gas contains about 0.1 to 10 percent oxygen.

References Cited in the file of this patent UNITED STATES PATENTS 1,721,959 James July 23, 1929 2,109,700 James Mar. 1, 1938 2,476,417 Jarnagin July 19, 1949 

1. METHOD FOR PREPARING PARTIAL OXIDATION PRODUCTS HAVING SATISFACTORY COLOR WHICH COMPRISES; PARTIALLY OXIDIZING NORMALLY NON-GASEOUS HYDROCARBON MATERIAL IN LIQUID PHASE IN AN OXIDATION ZONE TO OBTAIN SAPONIFIABLE PRODUCTS; REMOVING THE PRODUCTS FROM SAID OXIDTION ZONE; AND CONTACTING THE PRODUCTS AT ELECVATED TEMPERATURE NORMALLY PRODUCING EXCESSIVE DISCLORATION OF THE PRODUCTS IN LIQUID PHASE WITH FREE-OXYGEN CONTAINING GAS UNDER PARTIAL OXIDATION CONDITIONS PROVIDING AN INCREASE 